ABSTRACT Antiretroviral therapy (ART) for people living with HIV (PLWH) dramatically improves health and reduces onward HIV transmission, but suboptimal HIV care engagement has prevented these benefits from reaching large numbers of PLWH. HIV care continuum estimates suggest that nearly half of US PLWH are not retained in continuous HIV care, indicating that effective interventions for improving HIV care engagement are urgently needed. The proposed study seeks to inform the development of such interventions through the following specific aims: 1) characterize HIV care attendance and its relationships with time-varying care engagement drivers in the 18 months following HIV diagnosis; and 2) estimate HIV incidence reductions achievable through targeted interventions aiming to improve HIV care engagement. To achieve these aims, we will leverage a strong, long-standing collaboration between the University of North Carolina and the North Carolina (NC) Division of Public Health to conduct a population-based, prospective cohort study of PLWH in NC. This prospective, population-based cohort approach is explicitly designed to overcome key limitations of existing care engagement research, which is typically confined to a single clinic, clinic network, or surveillance system and is usually limited in terms of the time periods, care predictors, and/or transmission risk behaviors assessed. We will start follow-up near the time of HIV diagnosis and collect longitudinal information on HIV care encounters, transmission risk behaviors, and demographic, psychosocial, clinical, and structural barriers/facilitators to HIV care engagement via quarterly surveys for 18 months. We will supplement self-reported data with data from clinical settings and HIV surveillance programs to capitalize on the strengths of each data source, minimize missing data, and maximize the breadth of information available for analysis. In Aim 1, we will use cohort data on care encounters and multilevel care engagement predictors to describe early HIV care patterns and identify time-varying drivers of engagement. The results of this first aim will provide critical information for the design of care engagement interventions that target the right strategy to the right people at the right times. In Aim 2, we will use cohort data on transmission risk behaviors, ART use, and viral suppression to mathematically model HIV transmissions and the projected impact of targeted interventions designed to increase care engagement. The expected outcome will be information for designing, targeting, and prioritizing intervention strategies for optimizing HIV care engagement and transmission prevention. We will seek to conduct future, larger-scale cohort studies and intervention trials of the strategies found to be most worthy of further study, with the ultimate goal of increasing care engagement to maximize the clinical and preventive benefits of ART.